CVE-2025-10531: 
NixOS vulnerability analysis and mitigation

CVE-2025-10531 is a security vulnerability affecting Firefox versions prior to 143 and Thunderbird versions prior to 143. The vulnerability was discovered by security researcher Nikolaos Mourousias and was disclosed on September 16, 2025. It has been identified as a mitigation bypass issue in the Web Compatibility: Tooling component (Mozilla Advisory).

The vulnerability has been classified as having a moderate impact according to Mozilla's security advisory. It specifically affects the Web Compatibility: Tooling component of both Firefox and Thunderbird applications (Mozilla Advisory, Thunderbird Advisory).

The vulnerability has been rated with moderate severity impact. In Thunderbird specifically, Mozilla notes that these flaws cannot be exploited through email since scripting is disabled when reading mail, but they remain potential risks in browser or browser-like contexts (Thunderbird Advisory).

The vulnerability has been patched in Firefox 143 and Thunderbird 143. Users are advised to update their applications to these versions to mitigate the security risk (Mozilla Advisory, Thunderbird Advisory).